This proposal is to study insulin secretion and the metabolic response of recipient rats made diabetic by streptozotocin after transplantation of fetal pancreases. Diabetes follows intravenous injection of streptozotocin in doses of 75 milligrams/kg body weight. After diabetes is established fetal pancreases of syngeneic strain will be placed beneath the kidney capsule and the metabolic response of the recipient rat will be measured by blood glucose concentration and urine volume and glucose content. After establishment of a reproducible model of response in syngeneic transfers, the results of allogeneic transfer in in-bred strains of rats of known histoincompatibility will be determined. Effects of overcoming rejection across histocompatibility barriers by blocking antibody will be tested. Methods for tissue serological typing and matching by mixed lymphocyte culture of fetal human tissues will be developed using aborted human fetuses.